Micro-scale devices or systems such as integrated circuits (ICs), opto-electronic and photonic devices, micromechanical devices, micro-electro-mechanical systems (MEMS), micro-opto-electro-mechanical systems (MOEMS or optical MEMS), chip-based biosensors and chemosensors, microfluidic devices (e.g., labs-on-a-chip), and other articles characterized by micron- and sub-micron-sized features often require the use of high-density electrical interconnect schemes for transmitting signals. The interconnect scheme can consist of a cross-bar array of communication lines located at different levels or planes of a micro-scale structure. For example, one level can contain an arrangement of parallel input lines, while another level can contain an arrangement of parallel output lines oriented orthogonal to the input lines. Any two levels of communication lines can be electrically isolated from each other by embedding the lines in dielectric material and/or building a dielectric layer between the levels.
It is desirable to integrate interconnect schemes with the architecture of such micro-scale devices and, in particular, array devices such as DC micro-relays. However, the electrical current carried through a high-density interconnect arrangement of communication lines can give rise to self-heating. Joule heating (h) is associated with the conduction of current (i) over time (t) through communication lines made from a material having a resistance (r), and can be expressed by Joule's law: h=i2 rt. Joule heating gives rise to elevated temperatures in the various layers of a micro-scale structure and steep thermal gradients in dielectric layers. The heat energy dissipated through a micro-scale structure, particularly a MEMS device built over an interconnect scheme, can damage the components of the structure or impair the performance of those components. Depending on the current load, the elevated temperatures attained can result in thermally induced stress-related issues such as warping.
For example, a MEMS device can include a DC switch that utilizes a parallel-plate capacitor architecture for actuation purposes. A thermally-induced curvature in the substrate of this MEMS device could result in the shorting of the DC switch. As another example, in the case of very high current loads that are likely to occur during a power surge, the temperatures attained could be high enough to heat certain materials of a micro-scale device up to their melting point or transition temperature, and thus cause destruction of the entire device. Thus, while it is desirable to integrate a high-density interconnect scheme with a micro-scale device, the inclusion of the interconnect scheme would restrict the operating range of the device and raise concerns about the reliability of the device.
It would therefore be advantageous to provide an interconnect device that is structured to reduce maximum operating temperatures, thereby enabling the interconnect device and the useful features it provides to be integrated with a wide variety of micro-scale devices.